Electric arc welding



March 1965 R. P. CULBERTSON 3, ,074

ELECTRIC ARC WELDING Filed Oct. 3, 1962 \Wood Cross-Tie M54219 9 24zwwmw Bed (sfone) (Q /2W/ (1/6. -Ra|| X as ull" Weld Mefal Sieel SheaihW 42 Filler M aferial Conialmng Amorphous M Carbon INVENTOR. RUSSEL P.CULBERTSON BY aaww e ATTORNEY United States Patent 3,175,074 ELECTRICARC WELDING Russel l. Culbertson, Kokorno, Ind, assignor to UnionCarbide Corporation, a corporation of New York Filed Oct. 3, 1962, Ser.No. 228,037 8 Claims. (Cl. 219-l46) This invention relates towork-in-circuit electric arc welding, and more particularly to the artof hard-facing articles subjected to severe wear, such as railroadrails.

The invention provides a cored-wire electrode for semiautomatic electricarc welding, especially building up worn rail ends in situ, without theneed for any shielding gas stream, in which the core-material is apowder-blend of -30 screen size metal powder and free carbon in anamorphous state, the particles of which approach the molecular by virtueof the grinding which takes place with the metal powder in themixing-blending process which also uniformly distributes and disbursessuch carbon throughout the core. As a result, the welding operation issimpler, cheaper, and may be done by even inexperienced welders.Furthermore, the weldments are superior in that they withstand batteringin severe railroad service for a much longer time than was possibleaccording to the prior art even in the cases of CO and argon stream areshielding.

In industry, the replacement and maintenance of components due to wearof metal parts is a formidable and costly problem. The railroad industrymust constantly service or replace rails because of wear. Only a slightamount of wear is caused by the wheels rolling over the rails. At therail ends, however, wear is excessive because of the batter of thewheels as they pass over the rail joint and drop on the succeeding raiAs wear increases, the batter becomes more severe, thereby acceleratingmore wear in a vicious circle.

The constant batter of the wheels on the rail ends causes loosening ofrail ties, an uneven ride of the railroad cars and promotes theformation and growth of transverse fissures, detail fractures and gaugecorner shelling of the rails, which often result in rail failure inservice. Such types of rail damage usually originate as small internalimperfections in the rail that produce minute cracks, these cracks growlarger by a fatigue failure mechanism caused by stresses, vibrations andbatter, especially at the rail ends.

Several means are available to reduce rail failures described above. 1)Reduction of the number of rail joints by increasing rail lengths from33 feet to 39 feet or more. (2) Rail joints may be also reduced by theformation of continuous rail by joining rail ends by thermit welding andresistance butt welding, which are costly and cumbersome to perform atthe scene of installation. (3) Rail failures may be reduced by heating,quenching and tempering the entire rail or at least the rail ends.However, because rails are produced by hot rolling into final shape inlengths of over 33 feet, such heat-treatment would be costly anddifficult and may result in warpage of the rail. (4) The most practicalavailable means of reducing the above-mentioned rail failures appears tobe in fusion coating the worn areas of the rail ends with an alloy thatis resistant to wear and compatible with the composition of the originalrail as shown in Table I.

ice

TABLE I Composition and hardness of typical rails [U.S. Standard Rails]1 Compiled data representing about heats of standard rails from eightrailroads.

This invention provides novel filled tube rod or wire electrodes,preferably in the form of coils which are applied by the open-arcprocess. The electrode is preferably made according to the method ofStoody Patent No. 1,629,- 748, dated May 24, 1927. One of theoutstanding advantages of the open-arc process is the elimination of anyneed for an inert gas supply and attendant equipment. This feature isespecially desirable for welding and hardsurfacing operations that areperformed away from the shops, for example, field maintenance of railwaytrack members. In the open-arc process there is no gas shielding;therefore, the tube electrode filler usually contains an organic powder(wood or other vegetable products) or an inorganic powder such assiderite (FeCo or limestone (calcium carbonate). Such powders areconsumed and/ or Sublimated by the heat of the arc, thereby providing aneffective gaseous envelope (primarily CO and CO to protect the arcstream and the deposit puddle.

The use of the general class of organic and inorganic powders mentionedabove has limitations that prevent a broader exploitation of theopen-arc process, which is more efficient and more economical than othercomparable welding methods.

Tube electrodes that contain the above-mentioned organic and inorganicfiller materials, which provide a protective gaseous envelope inopen-arc processes, are used for many applications in industry. However,deposits made from prior materials often vary widely in composition andphysical and mechanical properties. Because of such prior limitations,the railroad industry has preferred that right-of-way rail welding andsurfacing be performed by inert-gas-shielded methods. Such methodsassure more uniform deposits of the highest degree of quality anddependability, thus minimizing rail failures. Thus, there is a greatneed for a tube rod that meets the stringent requirements of therailroad industry and may be applied by the open-arc process moreefiiciently and more economically.

The primary object of this invention is to provide an improvedcomposition for filler tube rods or coils.

Another important object is to provide .a welding or surfacing electrodesuitable for application on railway right-of-way track members by theopen-arc process.

Another object is to provide an improved tube rod or coil that willconsistently produce deposits of the highest degree of quality anddependability.

Still another object is to provide an improved semi automatic arcWelding process.

Other aims and objectives of this invention will become apparent fromthe present disclosure.

These and other objects are obtained through the provision of a novelhard-facing tube rod consisting of a mild steel sheath and a fillermaterial that is powderb lended, preferably according to Fischer PatentNo. 2,514,126, dated July 4, 1950. Such material comprises inweight-percent, about 23 percent chromium, 3 percent combined carbon,and 2 percent tree carbon, the particle size of which approaches themolecular, 0.80 percent silicon, 2.75 percent manganese, 2 percentmolybdenum, .70 percent aluminum, 1 percent titanium, and the balanceiron and incidental impurities together with less than 1 percent of anactive fiuxing agent. The ratio of sheath to filler material should beabout 70 to 30 by weight. The fused deposit of the tube rod consists of4 to 7 percent chromium, .5 to 1.2'percent carbon, .5 to 1.25 percentmanganese, .4 to 1.2 percent molybdenum, .5 percent maximum silicon, upto .1 percent aluminum, up to .25 percent titanium, and the balance ironand incidental impurities, with traces if any, of the fluxing agent.Proper blending of the filler materials is an improvide impact strength,wear resistance, and hardness. Although chromium, manganese andmolybdenum may each vary in content, as shown in Table 2, it ispreferred that their total content in the deposit should be not lessthan about 6 percent. Silicon may be present as an impurity up to about0.5 percent. Aluminum and titanium may be present as residual elementsup to about .1 and .25 percent, respectively, in the deposit; however,these elements are usually lost during the hard-facing operation. Thealuminum-titanium compound in the filler serves as a deoxidizing andflexing agent. Potassium titana-te is present in the tiller also as afluxing agent. Carbon is essential in the deposit alloy principally as acarbide former to provide hardness, wear resistance, and strength. Thebalance of the deposit alloy is iron and the usual impurities associatedwith this class of alloys; i.e. phosphorus, sulphur and the like. Theseimpurities should be kept at a very low content, consistent with therequirements of railroad mainline specifications.

The filled tube rods may be flash coated with copper to improveelectrical contact, inhibit rust and to act as a lubricant for feedingmechanism. Preferably, the mild steel strip is copper coated before itis fashioned as the tube sheath.

portant and critical feature of the present invention. TABLE 2 in the 0Composition of filler material FIG. 1 is a wiring diagram illustratingsuitable means for carrying out the invention; Amount A t L In: 8 FIG. 2is an enlarged cross-sectional view of the tube Added POP Material $235rod, and cent by Weight Size FIG. 3 is a fragmentary plan view of a railjoint. As shown in FIG. 1, when the end of tube-rod elec- 3M0 ggig gflgs ggg g a mesh- I en a .1 trode 10 is brought into contact with the topof rail 12 i 5 to fiuml g t to be repaired, a welding circuit isestablished which in- 3 30 SW1 g g yg g Q P no mesh r I "1 "an OW OS- 0eludes D.C. source 14, conductor 16, relay coil 18, feed phor us Grime).b rolls 20, tube-rod electrode 10, rail 12, and ground lead Manganese,39 P r t Carbon, 7.00 percent ina omnin. 22. This energiaes welding arc2e, and at the same time, sal m percent max mum. closes relay contacts26, energizing rod-feed motor 23 gf ig 010 Percent maxi from generator30, which drives rod-feed rolls 20 feed- 450 Ferrorriolyhdenurn s0 mesh.ing tube-rod electrode 10 from a rod 32 toward the are Mgg vgadenum,02.00 to 61.00pm- 24 as long as the end of such electrode is held nearthe Silicon, 0.20 to 0.60 percent. i 12 Carbon, 0.018 to 0.064 percent.

. Copper, 0.13 to 0.21 percent. The operator merely moves guide tube 34through Sulphur, 0.02 to 0.10 percent. handle 36 to apply weld metal 33,FIG. 3 on the bat- 52 ilg Pggf gg g g ff ggg g g i v J v tered anddepressed area oi the rail end as may be re- 4. percent maximum. lquired to complete the necessary build-up. i gg B011 9100 98mm As shownin FIG. 2, the tube-rod electrode 10 con- Carbon, 0.08 percentniaxiinum. sists of a steel sheath 40 containing the filler material g sg s 0.20 percent maxi- 42 Of the invention. gulphur, 0.025 percentmaximum.

a rz 0 To obtain desired proportion of elements in the filler Q9 ggrfggjpercent material, ingredients in the form of -30 screen size 100 A1 i pr -ar m- 1 powder, as shown in Table 2, are blended thoroughly, s 6 6521E 25: A00 mes and incorporated within a mild steel sheath. A suitablemummy 53-00 W 54-00 139mm g Iron, 0.50 to 1.00 percent. sheath materialis the common SAE 1010 steel. Silicon, 0.0; to 0.09 percent.

Chromium is present in the iron-base alloy deposit as o 200 H g,; ff{-?ffi i, a carbide former to rovide stren th and hardness. Man- PotasSiumTitanflte 200m@S11- P g ganese and molybdenum are present in the depositto TABLE 3 Range of Compositions, in w/o Filler Material Rail DepositPreferred Broad Optimum Preferred Broad Optimum gr( combined) bined) Fe(tree) Best results are obtained when two percent by weight of amorphouscarbon is blended into the filler powder as free carbon. Free carbon inthe filler mixture stabilizes the arc, thereby promoting a steadyburn-oil rate. By an undetermined mechanism, the amorphous carbon tendsto stabilize the arc. The stabilized arc provides a more uniform controlof the fusion of the weld deposit, and especially the depth ofpenetration at a lower amperage. (Heretofore, high amperages had to beused to make up losses due to unstable arc performance.)

The burn-01f rate refers to the rate of consumption of the tube-rodduring the depositing operation. The stabilized arc promotes a uniformrate of deposition, and therefore, the process is less complicated andmay be performed by semior even unskilled operators. Further, theuniformly high quality of the deposit renders it suitable for railroadright-of-way maintenance.

Lampblack is especially eifective as the amorphous carbon addition,especially when blended, so that its form approaches molecular size,with the other powdered ingredients of the filler. The exact mechanismunderlying criticality of lampblack in the composition is not clearlyunderstood. It is tentatively proposed that the amorphous carbon, whenadded in the form of lampblack, is combined with oxygen in the heat ofthe arc, thereby providing a C envelope to protect the deposit puddle.Other forms of carbon that are crystalline, such as graphite, carbondust, carbon ash products, and the like, do not readily provide the COenvelope.

Equivalents of lampblack may be deposit products of the flame resultingfrom the incomplete combustion of carbonaceous materials or gases. Thesemay include flame deposits of acetylene, natural or producers gas,petroleum products and the like. It is believed that the amorphousstructure of such soot deposits combines more readily with oxygen toform the CO envelope. Further, the amorphous carbon is consumed duringthe hard-facing operation, and does not deleteriously altect the carboncontent of the deposited alloy. Experiments show that, when crystallinecarbon alone is used as the free carbon in the tube rod in open-arcoperations, the carbon behaves erratically in the puddle and yields analloy with an unpredictable carbon content. Since the presence ofamorphous carbon provides an oxygen-deficient atmosphere, when carbonadditions to the deposit are desired, crystalline carbon may be added tothe tube-rod filler powder along with the amorphous carbon, insufiicient quantities to obtain a predictable carbon content in thedeposit. This constitutes a further improvement in the art.

Moreover, it is believed that the amorphous carbon is not readily wettedby the molten metal and, therefore, is less likely to be incorporatedinto the composition of the deposit alloy. The amorphous carbon willtend to float on the puddle because of its lower specific gravity. Acomparison of the properties of the two forms of carbon is given inTable 4.

TABLE 4 Physical and chemical properties of carbon 6 porous nature ofthe amorphous carbon. In theory, it is expected that the amorphouscarbon, being more porous and, therefore having a greater surface area,combines with oxygen in the ambient atmosphere more readily than doesthe crystalline carbon, which is more dense. In addition, the particlesof amorphous carbon are inherently very minute when compared tocrystalline carbon, which must be mechanically crushed and pulverizedinto small particles.

EXAMPLE I A mixture of filler material for a hard-facing tube rod wasprepared in accordance with the preferred composition as shown in Table2. After blending the mixture for about one hour in a twin-shell type ofblender, the material was processed into a %4ll'lCl1 diameter rod. Theproportion by weight of the S.A.E. 1010 steel sheath to filler materialwas 70 to 30. The method of preparing various sizes of tube-rod (forexample, /1eto -inch diameter), while maintaining an establishedsheath-tofiller ratio is well known in the art.

The tube rod was prepared in the form of a coil with a flash coating ofcopper for the reasons mentioned above. Methods of flash plating themild steel sheath material are well known in the art. The copper platingis very thin (less than 1 mil) and is probably vaporized and/ oroxidized in the heat of the arc. The residual copper content, if any, isonly in trace quantities and does not adversely affect the depositquality.

The tube-rod was Open-arc deposited on a plate of SAE 1020 steel with awelding current of 275 amperes and 30 volts (direct current-reversepolarity). To obtain a smooth deposit, the weld beads were overlappedapproximately 25 percent. Three layers were deposited; the entiredeposit was then cold-work hardened by peening. Hardness values for eachlayer and the work-hardened deposit are shown in Table 5.

Duplicate compositions were prepared to check the eproducibility of thetube-rod. The compositions are identified as Heat No. 7 and Heat No. 36.Each heat was prepared into a number of coils. Hardness values ofdeposits from random coils are shown in Table 5.

TABLE 5 Composition and hardness of selected heats Specific gravitySublimation Temperature, C Boiling Point, 0 Heat of Combustion,Fg-CaL/gn. Heat of Oxidation, Gals/gramatom. Thermal Conductivity:

Btu/hrs. sq. it./ F./it 60. C GS units .0117. Soluble in liquid ironYes.

The greatest difference in physical properties between amorphous andcrystalline carbon appears to be in thermal conductivity. This isprobably due to the extremely Heat No. 7 Composi- Heat No. 36Composition, weight percent tion, weight percent Filler Deposit FillerDeposit Powder Powder Hardness, Re Hardness, Re

Range Average Range Average Layer No.1

Total Rangm 51-53 47-60 Average 56. 2 54. 3

I I EXAMPLE 2 While the hardness of a deposit is only a good indicationof wear properties, the ideal evaluation of rail characteristics ispossible only in actual service of mainline track over a prolongedperiod of time. Since such testing would be impractical (and evenhazardous), the American Association of Railroads (AAR) has erected arolling load testing apparatus specifically designed for testing variouscharacteristics of rails. In a testing program conducted by AARpersonnel, the deposits of the tube-rod of this invention (as describedin Table 2) and three typical commercial (known) welding electrodes weresubjected to the rolling load test as mentioned above. All test depositswere made on random worn rails by AAR personnel according to standardrailroad practices. Data obtained from the tests are given in Table 7.The data show that the deposit of the tube-rod of this invention, AlloyA, was superior to the alloy deposits of commercially known electrodesfor railroad service. The tests are normally terminated at 5,000,000cycles, which is considered to be optimum endurance, or when excessivewear or (an anomaly is noted. It is particularly significant that thewear rate of Alloy A was appreciably lower than wear rates of theothers.

The favorable results of the rolling load tests on Alloy A warrantedadvanced testing. Several miles of mainline track of an eastern railroadwas designated as a testing site where Alloy A was deposited on wornrail ends by the open-arc process. The deposits are continuallyinspected and evaluated to determine the wear and endurancecharacteristics under actual conditions of use in mainline track.

The results of testing the tube-rod in this Example indicate that thetube rod of this invention is highly suitable for rail end hard-facingwith a high degree of dependability and reproducibility as required bythe railroad specifications.

55 What is claimed is:

1. An arc welding tube rod filler material composed of a --30 screensize powder-blend of the following ingredients, by weight:

Percent Cr 18-30 C (combined) 1-5 C (free) 0.5-3

Si 054:5 Fe (combined) Bal. Fe (free) 30-60 wherein such free carbon isin an amorphous state, such as lampblack, of almost molecular particlesize.

2. An arc welding tube rod filler material composed of a --30 screensize powder-blend of the following ingredients, by weight:

wherein such free carbon is in an amorphous state, such as lampblack, ofalmost molecular particle size.

3. An arc welding tube rod filler material composed TABLE 6 AAR rollingload test results Hardness, BI-IN A ppro nmate Completed Deposit WearRates, Y Test Deposit Cycles Wear, Mils mils per 10 Rail cycles BeforeTest After Test The examples and use of the tube rod of this inventionas described herein constitute a preferred embodiment of the inventionto provide a clear understanding of the invention, and are not to beconstrued as limitations except as defined in the appended claims. Thetube rods of this invention may be used to provide weldments forhardfacing or joining metal parts other than railway hardware. Weldmentdeposition may be accomplished by other known work-in-circuit electricarc processes, although the open-arc process is preferred. Other usesand modifications within the scope and spirit of this invention willsuggest themselves to persons skilled in the art.

of a 30 screen size powder-blend of the following ingredients, byweight:

wherein such free carbon is in an amorphous state, such as lampblack, ofalmost molecular particle size.

4. An arc Welding tube rod consisting of a mild steel sheath containinga core of filler material as defined by claim 2, in which the proportionby Weight of the steel sheath to filler material is of the order of 70to 30.

5. Method of hard facing Work composed of steel, which comprisesenergizing an electric Welding are between the end of tube rod asdefined by claim 4, and such Work with a source of direct current atreverse polarity in circuit therewith, and feeding said tube rod towardsuch are to obtain a smooth fused deposit of alloy from the tube rodthat is welded to the Work, consisting of a -30 screen sizepowder-blended mixture, of 4 to 7 percent chromium, .5 to 1.2 percentcarbon, about half of which is in an amorphous form having an almostmolecular particle size, .5 to 1.25 percent manganese, .4 to 1.2 percentmolybdenum, .5 percent maximum silicon, up to .1 percent aluminum, up to.25 percent titanium, and the balance iron and incidental impurities,with traces, if any, of the fiuxing agent.

6. A hard-facing tube rod consisting of a mild steel sheath and a -30screen size powder blend of filler mate rial comprising, inweight-percent, about 23 percent chronium, 3 percent combined carbon and2 percent free carbon, 0.80 percent silicon, 2.75 percent manganese, 2percent molybdenum, .70 percent aluminum, 1 percent titanium, and thebalance iron and incidental impurities together with less than 1 percentof an active fiuxing agent, in which the ratio of sheath to fillermaterial is about 70 to 30 'by Weight, and said free carbon in anamorphous state is uniformly powder-blended with the other ingredientsof the filler material so that the particles of free carbon in suchblend approach molecular particle size.

7. A Work-in-circuit Welding tube rod filler material containing a -30screen size powder-blend of chromium, manganese, molygdenum, silicon,and a fluxing agent said powder-blend comprising of, by weight, about 50percent iron powder and about 2 percent free carbon, wherein such freecarbon is in an amorphous state; and incidental unavoidable impuritiesnormally found in articles of this class; said free canbon having aparticle size that approaches the molecular.

8. An arc welding electrode consisting of a wire provided with a corecomposed of the material set forth in claim 7.

References Cited in the file of this patent UNITED STATES PATENTS1,629,748 Stoody May 24, 1927 1,704,978 Knott Mar. 12, 1929 1,745,267Pennington Jan. 28, 1930 1,942,364 Rood Jan. 2, 1934 3,029,165 Kihlgrenet a1. Apr. 10, 1962

7. A WORK-IN-CIRCUIT WELDING TUBE ROD FILLER MATERIAL CONTAINING A -30SCREEN SIXE POWDER-BLEND OF CHRONIUM, MANGANESE, MOLYGDENUM, SILICON,AND A FLUXING AGENT SAID POWDER-BLEND COMRISING OF, BY WEIGHT, ABOUT 50PERCENT IRON POWDER AND ABOUT 2 PERCENT FREE CARBON, WHEREIN SUCH FREECARBON IS IN AN AMORPHOUS STATE; AND INCIDENTAL UNAVOIDABLE IMPURITIESNORMALLY FOUND IN ARTICLES OF THIS